The present invention relates to a variable compression ratio device for an internal combustion engine.
Disclosed is a variable compression ratio device for an internal combustion engine which can change a compression ratio in order to achieve high efficiency and low fuel consumption. For example, in the variable compression ratio device, an eccentric sleeve is rotatably inserted between a large end of a connecting rod and a crank pin of a crankshaft, and the eccentric sleeve rotates due to the rotation of the crankshaft. The position of the crank pin with respect to a support hole of the connecting rod is changed due to the rotation of the eccentric sleeve, and the compression ratio switches between a high compression ratio and a low compression ratio (for example, refer to Patent Documents 1 and 2).
The rotation position of the eccentric sleeve is fixed to a predetermined rotation position using a stopper or the like that is mechanically operated so as to fix the compression ratio. In addition, the rotation position of the eccentric sleeve is fixed by increasing the frictional force of the eccentric sleeve with respect to the support hole of the connecting rod using oil pressure.
However, since the rotation of the eccentric sleeve is dependent on the rotation of the crankshaft (operation of the internal combustion engine), the eccentric sleeve rotates in one direction, and is likely to be subjected to inertial force. In addition, the rotational speed of the eccentric sleeve changes due to combustion pressure. For this reason, there is a problem in that the rotation position of the eccentric sleeve cannot be accurately fixed because responsiveness in fixing the rotation position changes when the rotation position of the eccentric sleeve is fixed and thus the compression ratio is fixed.
[Patent Document 1] JP-A-6-241058
[Patent Document 2] JP-A-2000-64866